It is a known practice to produce such a duct in two distinct and separate parts secured to one another in a manner so as to define a closed internal volume extending between an inlet of the duct, connected for example to an air conditioning device, and at least one outlet of the duct that opens into an opening formed in the structural element. The fabrication in two parts of the duct allows for forming each of these parts in one single step of injection without any particular difficulty in the demoulding of these parts.
However, it should be ensured during the assembly by joining of the two parts to one another that the duct is sealed between the inlet and the outlet in order to prevent any leakage of air between the two parts. Such air tight sealing is usually ensured in an optimal manner by welding the parts to each other around the internal volume.
Similarly, in particular for ensuring the sealing of the duct between its outlet or outlets and the one or more corresponding openings in the structural element, it is a known practice to weld the assembled duct to the structural element.
Thus, the assembly of the duct itself and the assembly by joining of the duct to the cladding structural element requires two separate steps of welding and of providing on the assembly lines two distinctly separate tools and of interchanging the tools during the course of the assembly so as to carry out the two steps of welding. The assembly is thus costly, far from practical to implement and reduces the rates of production of the lining element.